I have never sprayed Duracoat, but it is just paint......it should stick fine as long as you use the proper primer.....I'd probably sand it or bead blast it first and then use a compatible etching primer before painting.

For really neat coatings for aluminum do a search on " home anodizing of aluminum " . The info is astounding and the process simple and cheap . I don't know if you saw the latest wild child offering on 6mmbr , a really cool space gun that has some anodized aluminum parts and the inventor of this rig ( it has a magnetic tuner no less ) anodized the parts himself .

The best search provided article I read was by a Brit and he was thorough . If you do it let me know . I'm still playing with aluminum myself .